A major hurdle in achieving a cure for HIV-1 is the existence of reservoirs of persistent viral infection, with resting memory CD4+ T cells being the largest and best studied. In these cells, HIV-1 rests as a latent provirus refractory to antiretroviral therapy (ART) and invisible to immune surveillance, which can be reawakened and spread the infection. In recent years there has been a push to develop therapies targeting latently infected CD4+ T cells. The shock and kill approach seeks to flush latent provirus with anti-latency drugs that do not cause global T cell activation, and in the presence of ART to prevent the flushed virus from spreading the infection. However, recent evidence suggests that this approach may be inadequate. Our long-term goal is to develop strategies to directly target and deplete latently infected CD4+ T cells without reactivating the provirus. Our central hypothesis is that surface markers differentially expressed on latently infected CD4+ T cells may be used to achieve that goal. With the support of an NIH-funded grant, we profiled the transcriptome of latently infected and uninfected CD4+ T cells generated with our in vitro latency model, and we identified 33 differentially expressed surface markers. We also found that one of the receptors identified in the microarray screen - CD2 - is expressed at higher levels on latently infected resting memory CD4+ T cells of HIV-1 subjects under suppressive ART. The present application proposes to further pursue these studies with the aim of establishing a panel of cell surface markers that when used in combination will allow to identify with high specificity latently infected resting memory CD4+ T cells in vivo. Thus, in Specific Aim 1 we propose to use our in vitro latency model to validate all the surface markers differentially expressed in the microarray study, and to understand why latently infected cells present that specific expression profile. Specific Aim 2 proposes to validate the markers identified in the previous specific aim, and to generate a panel of surface receptors to define with high specificity latently infected CD4+ T cells in peripheral blood and lymph nodes of HIV-1 patients. The expected outcome of these studies is the establishment of a panel of cell surface markers that in combination will define with high specificity latently infected resting memory CD4+ T cells in vivo. These markers can be used to monitor the size of the latent reservoir in the clinical setting, to enrich latently infcted CD4+ T cells in the laboratory setting, and possibly as a therapeutic target to deplete the latent reservoir without reactivating the provirus. This work is a partnership with Nicolas Chomont at VGTI-Florida, who developed ultra-sensitive techniques to measure integrated HIV-1 provirus in clinical samples, and viral RNA after ex vivo reactivation.